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Abstract:

This invention relates to a method for conducting film coating on the
surface of spinning circular workpiece under action of gas pressure, and
nozzle utilized in the same. Circular workpiece to be coated is held on a
rotating mechanism, and a feedstock loading machine having a nozzle,
which is capable of guiding redundant feedstock and overflowing in a
specific direction, is set to have a 100 μm gap with the circular
workpiece. When the rotating mechanism is rotated, the polymer solution
is precoated on the surface of the circular workpiece, and when gas valve
is opened, the polymer solution is squeezed to a predetermined thickness
by an annular high pressure gas-stream formed on the periphery of a
cylinder, produced from the high pressure gas released.

Claims:

1. A method for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure, wherein coating material
is fed onto the inner or outer surface of a circular workpiece conducting
self-spinning, an annular gas-stream surrounding in the radial direction
of said circular workpiece in such a manner that the coating material on
said circular work is squeezed by the gas-stream so as to be distributed
in even and flat manner.

2. The method for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 1,
wherein the gap between said circular workpiece and the annular
gas-stream is 0.5 mm to 2 mm.

3. The method for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 1,
wherein the material of the circular workpiece is one selected from:
medium-carbon steel, high-carbon steel, any polymer material, organic
material, plastic material, semiconductor material, metallic material,
quartz, glass material, ceramic material, inorganic material,
electrically conducting material, compound of any two above materials, or
compound of more than two above materials.

4. The method for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 1,
wherein the self-spinning action of said circular workpiece is conducted
by a rotating mechanism, and the rotating mechanism is a lathe.

5. The method for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 1,
wherein said coating material is selected from: organic photoresist or UV
resin, or any polymer material, organic material, plastic material,
compound of any two above materials, or compound of more than two above
materials.

6. The method for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 1,
wherein the gas of said annular gas-stream is selected from ordinary air
or pure nitrogen gas.

7. An apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure, at least comprising: a
rotating mechanism provided on the base frame, which has a chuck to
securely holding the circular workpiece; a translational mechanism
provided on said base frame, which has a guide portion for guiding said
translational mechanism to move toward the direction of the rotating
mechanism; an annular gas-stream generating device for producing annular
gas-stream, which is fixed on the translational mechanism, said annular
gas-stream being to act on the inner or outer surface of said circular
workpiece.

8. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 7,
further comprising a feedstock supply mechanism supplying desired coating
material at stable flow rate to the surface of said circular workpiece
through a discharge opening.

9. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 7,
wherein said circular workpiece has roundness and straightness below 2
μm obtained by precision lapping and polishing process.

10. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 7,
wherein a gap should be provided between said circular workpiece and said
annular gas-stream.

11. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 7,
wherein said rotating mechanism is a lathe.

12. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 7,
wherein said annular gas-stream generating device, in the case that said
surface is the outer surface of said circular workpiece, is formed by an
annular gas-ring having a plurality of gas pore arranged in equidistance
on the inner surface of said gas-ring, and each gas pore being in
communication with a gas inlet opening which is connected to a gas supply
source, when the gas supply source begins to supply high pressure gas, an
annular gas-stream being produced at the inner surface of said gas-ring
through the gas pores provided thereon.

13. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 12,
wherein said gas-ring includes a first member and a second member, said
first member being provided with a ring section on the base section and
said plural gas pores being provided on said ring section, while said
second member having a ring portion one end of which has an annular
flange extending toward the axis, and said gas inlet opening being
provided on said ring portion; said first member being fastened with the
second member together with a gasket interposed between the base section
of said first member and the ring portion of said second member, and with
another gasket interposed between the ring section of said first member
and the ring portion of said second member.

14. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 7,
wherein said annular gas-stream generating device, in the case that said
surface is the outer surface of said circular workpiece, is to provide an
annular slit on the inner face of the gas-ring, which is in communication
with a gas inlet opening connected to a gas supply source.

15. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 14,
wherein said gas-ring includes a first member and a second member, said
first member being provided with a ring section on the base section
thereof, while said second member has a ring portion one end of which has
an annular flange extending toward the axis and said gas inlet opening is
provided on the ring portion; said first member being fastened with said
second member together, one face of the base section of said first member
abuting against one end of the ring portion of said second member and a
gasket being interposed therebetween, while one end of the ring section
of said first member abuts against one face of the ring portion of said
second member and said slit is formed therebetween.

16. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 7,
wherein said annular gas-stream generating device, in the case that said
surface is the outer surface of said circular workpiece, is a hollow
cylinder body having an opening on one end thereof, the diameter of said
opening being slightly larger than that of said circular workpiece such
that said circular workpiece can be put on the hollow cylinder, the other
end of said cylinder body being an input end of high pressure gas.

17. The apparatus for conducting film coating on the surface of spinning
circular workpiece under action of gas pressure as claimed in claim 7,
wherein said annular gas-stream generating device, in the case that said
surface is the inner surface of said circular workpiece, has an annular
slit provided on the outer face of a cylinder body, said annular slit
being in communication with the interior of said cylinder body which is
connected to a gas supply source.

18. A nozzle, which is provided at the above discharge opening of said
feedstock supply mechanism as claimed in claim 8, wherein said nozzle has
a through passage, the end surface of said nozzle opposite to said
circular workpiece having a guide chute and a portion contacting with the
surface of said circular workpiece, said guide chute being communicated
with said passage.

19. The nozzle as claimed in claim 18, wherein said guide chute includes
a longitudinal guide chute and a transverse guide chute.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a method for conducting film
coating on the surface of spinning circular workpiece under the action of
gas pressure and a nozzle utilized in the same, more particularly to a
novel technology of uniformly coating a film having nano-scale thickness
on the surface of circular workpiece.

[0003] 2. Brief Description of the Prior Art

[0004] So far, there are substantially two methods of coating polymer
solution on the surface of circular workpiece, one is spray coating
method and the other one is blade coating method.

[0005] In the spray coating method, polymer solution (for example,
photoresist, UV resin) is firstly filled in spray gun, and then the
polymer solution is atomized into mist droplets after passing through the
spray gun, in turn the mist droplets is sprayed by high-pressure gas onto
the surface of a circular workpiece so as to finish the coating of the
circular workpiece. However, in the spray coating method, the outlet
pressure of spray gun has a Gaussian distribution (clustering around
center and is thin outside the center), hence mist droplets is failed to
be uniformly distributed especially when the mist droplets is in
nano-scale size. Therefore, the spray coating method cannot produce
polymer film having highly uniform thickness below 1 μm.

[0006] Referring to FIG. 13, the blade coating method is essentially to
use a doctor blade (7) to wipe redundant polymer solution (9) off the
surface of the circular workpiece (8), and the thickness of the polymer
solution coating is determined by adjusting the gap between the doctor
blade (7) and the circular workpiece (8). The method of wiping off
redundant polymer solution (9) by the doctor blade (7) can reach certain
extent of uniformity in the blade coating technology, but the doctor
blade (7) usually in mechanical feeding can hardly reach a distance of
less than 10 μm from the surface of circular workpiece, let alone a
displacement precision of 1 μm. Hence, a film of polymer solution
having thickness less than 1 μm cannot be achieved by the blade
coating method. Moreover, adhesion of the doctor blade (7) on the coated
film is often occurred during separation from the circular workpiece (8)
such that bad roundness is caused.

SUMMARY OF INVENTION

[0007] In view of the abovementioned disadvantages, the present invention
has proposed a technology for conducting film coating on the surface of
spinning circular workpiece under action of gas pressure as a substitute
for spray coating and blade coating method, so as to improve the
shortcomings of prior art.

[0008] The main object of the present invention is to provide a technology
exclusively used for coating circular workpiece, which has the following
advantages: polymer solution can be coated onto circular workpiece easily
and quickly, and the polymer solution film coated onto circular workpiece
has high-uniformity, high-roundness, super-thin film thickness, no seam
point.

[0009] One of the core technologies of the present invention is to control
thickness by gas pressure. For this purpose, a high pressure circular
gas-ring having high pressure air or pure nitrogen gas fed therein is
formed, and circular workpiece to be coated passes through the circular
gas-ring in self-spinning manner such that the high pressure air will
squeeze and thus homogenize the polymer solution coated on the circular
workpiece. In other words, the squeezing force is adjusted by controlling
gas pressure such that film thickness is subject to be changed.

[0010] Another one of the core technology of the present invention is to
control initial thickness by the gap between the discharge opening and
the circular workpiece. In the present invention, the circular workpiece
to be coated is held on a spinning mechanism for self-spinning, and the
discharge opening is arranged above the circular workpiece. The distance
between the discharge opening and the circular workpiece is appropriately
adjusted in such a manner that the feedstock contacts with the spinning
circular workpiece as soon as it is output from the discharge opening.
Hence, polymer solution is precoated on the circular workpiece by the
self-spinning of the circular workpiece, and redundant polymer solution
exceeding the height of gap can be wiped off by the discharge opening,
and then the redundant polymer solution is guided toward the radial and
axial directions. Thus, the discharge opening has both functions of
feedstock discharge and redundant feedstock wipe-off.

[0011] Another one of the core technology of the present invention is to
control initial thickness and uniformity by controlling the rotation
speed. In the present invention, the circular workpiece to be coated is
held on a rotating mechanism for self-spinning, and the rotation speed is
adjusted by a digital panel. The rotation speed determines the frequency
(in unit time) of circular workpiece's passage through the discharge
opening. The faster the rotation speed is, the bigger the frequency of
circular workpiece's passage through the discharge opening becomes and
the better the uniformity is.

[0012] Another one of the core technology of the present invention is to
control the uniformity by gap. The gas pressure distribution on the
surface of circular workpiece is directly influenced by the size of the
gap between the circular workpiece and the gas-ring. Under the same
rotation speed and the same gas pressure condition, optimum uniformity of
polymer solution film coated on the surface of the circular workpiece can
be obtained by a specific gap.

[0013] Another one of the core technology of the present invention is to
control the uniformity by gas-ring feeding speed. Inasmuch as the
redundant polymer solution is squeezed-off by high pressure air, the
speed of the circular workpiece passing through the circular gas-ring
determines the uniformity of the polymer film produced. The slower the
gas-ring feeding speed is, the longer the time of each point on the
circular workpiece passing through the squeezing by the gas-ring becomes.
Hence, the film thickness becomes more even.

[0014] Another object of the present invention is to provide a technology
by which different polymer solution can be coated on circular workpiece.
Therefore, both the coating material and the primer coating material can
be diversified so as to solve the problem encountered in the coating on
circular workpiece.

[0015] In order to achieve above objects of the present invention, a
method for conducting film coating on the surface of spinning circular
workpiece under action of gas pressure is provided, comprising at least
the following steps:

[0016] providing firstly circular workpiece made of any material (for
example, steel, glass, polymer), which has to meet some basic requirement
on its roundness and straightness;

[0019] adjusting the gap between the discharge opening and the circular
workpiece so as to obtain predetermined film thickness;

[0020] starting the rotating mechanism so as to allow spinning of the
circular workpiece, and the rotation speed is adjusted to a desired
value;

[0021] setting the pressure of the annular gas-stream, and the annular
gas-stream is moved forward in the direction of circular workpiece so
that the annular gas-stream is moved relatively with respect to the
spinning circular workpiece;

[0022] In this manner, the polymer solution is outputted from the
discharge opening and is coated onto the surface of the circular
workpiece along the direction of rotation by the spinning of the circular
workpiece. In turn, the annular gas-stream begins to squeeze the coating
material on the circular workpiece so as to reach desired thickness.

[0023] In order to achieve above object, an apparatus for conducting film
coating on the surface of spinning circular workpiece under action of gas
pressure of the present invention is provided, at least comprising:

[0024] a rotating mechanism used to hold the circular workpiece in place
and to move the circular workpiece into rotation;

[0025] a feedstock supply mechanism, which adjusts the flow rate and
stably supplies polymer solution to the discharge opening;

[0026] an annular gas-stream generating device moved by a translational
mechanism toward the direction of the circular workpiece, such that the
annular gas-stream generated by the annular gas-stream generating device
is moved relatively with respect to the spinning circular workpiece, and
the coating material coated on the surface of the circular workpiece is
squeezed by the annular gas-stream.

[0027] A nozzle is disposed on the discharge opening of the above
feedstock supply mechanism. The end surface of the nozzle opposite to the
circular workpiece has a guide chute and a portion contacting with the
circular workpiece. Redundant feedstock is guided and overflows along the
direction of guide chute, and the polymer solution is coated onto the
surface of the circular workpiece through the contact portion. In this
manner, the polymer solution can be evenly coated throughout the surface
of the circular workpiece so as to achieve the effect of surface coating
having good uniformity and flatness.

[0028] In the technology of conducting film coating on the surface of
spinning circular workpiece under action of gas pressure, the gas used in
the annular gas-stream can be high pressure air or pure nitrogen gas.
Lapping and polishing process should be conducted on the surface of the
circular workpiece so as to achieve roundness and straightness below 2
μm. Medium-carbon steel or high-carbon steel can be used as the
material for circular workpiece. A gap should be arranged between the
circular workpiece and the gas-ring.

[0029] Further in the technology of conducting film coating on the surface
of spinning circular workpiece under action of gas pressure, the annular
gas-stream generating device has a plurality of gas pore provided in
equi-distance on the inner surface of a gas-ring, and high pressure
gas-stream passes through the gas pores so as to produce annular
gas-stream.

[0030] Another preferred design of the annular gas-stream generating
device is to provide an annular slit on the inner surface of the
gas-ring, and high pressure gas-stream passes through the annular slit so
as to produce annular gas-stream.

[0031] Still another preferred design of the annular gas-stream generating
device comprises a hollow cylinder body having an opening on one end
thereof, the diameter of the opening is slightly larger than that of the
circular workpiece such that the circular workpiece can be put on the
hollow cylinder body. The other end of the cylinder body is an input end
of high pressure gas. In this manner, annular gas-stream can be produced
on the slit formed between the opening of the cylinder and the circular
workpiece.

[0032] The abovementioned annular gas-stream generating device is
implemented in film coating on the outer surface of circular workpiece.

[0033] Yet another preferred design of the annular gas-stream generating
device is to provide an annular slit on the outer surface of a gas-ring,
and high pressure gas-stream passes through the annular slit so as to
produce annular gas-stream. The annular gas-stream generating device is
suitably to be implemented in film coating on the inner surface of
circular workpiece.

[0034] The main purpose of utilizing a rotating mechanism (for example,
lathe) in the technology of conducting film coating on the surface of
spinning circular workpiece under action of gas pressure of the present
invention has the following advantages: 1. capable of adjusting rotation
speed in digital method. 2. capable of setting automatic gas-ring feeding
speed. 3. easy to hold the circular work in more stable manner.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG. 1 is a perspective outline view showing the first embodiment
of the present invention.

[0036]FIG. 2 is a view showing the structure of the first embodiment of
the present invention.

[0037]FIG. 3 is a side view showing the structure of the gas-ring and the
circular workpiece of the first embodiment of the present invention.

[0038]FIG. 4 is a perspective outline view showing the nozzle of the
present invention.

[0039]FIG. 5 is a perspective sectional schematic view showing the nozzle
of the present invention.

[0040] FIG. 6 is a schematic view showing the nozzle of the present
invention in using state.

[0041] FIG. 7 is a view showing the structure of the gas-ring of the
second embodiment of the present invention.

[0042]FIG. 8 is a side view showing the structure of the gas-ring and the
circular workpiece of the second embodiment of the present invention.

[0043]FIG. 9 is a side view showing the relationship between structure of
the gas-ring and the circular workpiece of the third embodiment of the
present invention.

[0044]FIG. 10 is a side view showing the relationship between structure
of the gas-ring and the circular workpiece of the fourth embodiment of
the present invention.

[0045]FIG. 11 is a schematic view showing the operation of squeezing the
coating material coated on the surface of a circular workpiece by the
annular high pressure gas stream in the first embodiment of the present
invention.

[0046] FIG. 12(a) is a table showing the film thickness measured on the
surface of the circular workpiece after coating in the present invention;

[0047] FIG. 12(b) is a graph plotted according to the data in FIG. 12(a);

[0048] FIG. 12(c) is a schematic view showing the measured points on the
surface of a circular workpiece after coating.

[0049]FIG. 13 is a flow chart showing the method for conducting film
coating on the surface of spinning circular workpiece under action of gas
pressure of the present invention.

[0050]FIG. 14 is a schematic view showing the coating of polymer solution
on the circular work by blade coating method.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0051] This invention discloses a method and an apparatus for conducting
film coating on the surface of spinning circular workpiece under action
of gas pressure, which can coat a coating material onto the outer or the
inner surface of circular workpiece quickly and uniformly so that
subsequent processes such as eximer laser process, photolithography
process can be conducted to define miniature patterns on the circular
workpiece for backside application. This invention will become more
apparent by the detailed description set forth below in conjunction with
accompanying drawings of FIGS. 1 to 13 and components' reference number.

[0052] Referring to FIGS. 1 to 3, an apparatus for conducting film coating
on the surface of spinning circular workpiece under action of gas
pressure of the present invention is shown, at least comprising:

[0053] a rotating mechanism (1) provided on a base frame (5), which has a
chuck (11) for securely holding a circular workpiece (2);

[0054] a translational mechanism (3) also provided on the base frame (5),
which has a guide portion (31) for guiding the translational mechanism
(3) to move toward the direction of the rotating mechanism (1);

[0055] an annular gas-stream generating device (4) for producing annular
gas-stream, which is fixed on the translational mechanism (3), the
annular gas-stream generating device (4) is driven by the translational
mechanism (3) to move toward the direction of the circular workpiece (2)
such that the annular gas-stream produced by the annular gas-stream
generating device (4) conducts relative movement with respect to the
spinning circular workpiece (2) so as to squeeze the coating material
coated on the surface of the circular workpiece (2).

[0056] Lapping and polishing should be conducted on the circular workpiece
(2) so as to reach roundness and straightness less than 2 μm. Hence,
the material of the circular workpiece (2) can be one selected from
medium-carbon steel, high-carbon steel, any polymer material, organic
material, plastic material, semiconductor material, metallic material,
quartz, glass material, ceramic material, inorganic material,
electrically conducting material, compound of any two above materials, or
compound of more than two above materials.

[0057] Moreover, this invention comprises a feedstock supply mechanism (6)
which supplies desired coating material at a stable flow rate onto the
surface of the circular workpiece (2) through the discharge opening (61).
The feedstock supply mechanism (6) can be a pressure pump of any type
capable of setting its flow rate. The discharge opening (61) is arranged
to be above the annular gas-stream generating device (4) by the
connection of a gas piping in such a manner that the discharge opening
(61) can be displaced accompanying with the displacement of the annular
gas-stream generating device (4), so as to coat the material onto the
surface of the circular workpiece (2).

[0058] Referring to FIGS. 4 to 6, a nozzle (62) having a passage (621) is
provided on the discharge opening (61), through which the polymer
material can be coated on the surface of the circular workpiece (2). The
end surface of the nozzle (62) opposite to the circular workpiece (2) has
a guide chute (622) and a portion (623) contacting with the surface of
the circular workpiece (2). The guide chute (622) and the nozzle (62) is
in communication with the passage (621) of the discharge opening (61).
The guide chute (622) further includes a longitudinal guide chute (622a)
and a transverse guide chute (622b), and the longitudinal and transverse
guide chutes (622a, 622b) are respectively in communication with the
passage (621) of the discharge opening (61).

[0059] When the feedstock supply mechanism (6) delivers coating material
through the discharge opening (61), the feedstock delivered is coated on
the surface of the circular workpiece (2) through the passage (621) of
the nozzle (62). As soon as the feedstock drops onto the surface, it is
closely contacted with the surface of the spinning circular workpiece (2)
through the contact portion (623) which functions as a doctor blade for
leveling the feedstock on the coated surface of the circular workpiece
(2). In the process of coating and leveling, the Redundant feedstock
wiped off by the contact portion (623) is further guided by the
longitudinal and the transverse guide chutes (622a, 622b) and is
overflowed along the direction of the same, i.e., along the forward
direction (transverse direction) and the rotational direction
(longitudinal direction). In this manner, the polymer solution can be
evenly coated throughout the surface of the circular workpiece so as to
achieve surface coating having good uniformity and flatness.

[0060] Furthermore, the nozzle (62) can be made of Teflon material
(polytetrafluoroethylene) so as to possess anti-acid-alkali and
anti-corrosion properties. The nozzle (62) can also be one selected from
any polymer material, organic material, plastic material, semiconductor
material, metallic material, quartz, glass material, ceramic material,
inorganic material, electrically conducting material, compound of any two
above materials, or compound of more than two above materials.

[0061] A preferred design of the annular gas-stream generating device (4),
referring to FIGS. 2 and 3, is formed by an annular gas-ring (41) having
a plurality of gas pore (411) arranged in equidistance on the inner
surface of the gas-ring (41), and each gas pore (411) is in communication
with a gas inlet opening (412) which is connected to a gas supply source
(413). When the gas supply source (413) begins to supply high pressure
gas, an annular gas-stream is produced at the inner surface of the
gas-ring (41) through the gas pores (411) thereon. Further, the gas-ring
(41) can be penetrated by the circular workpiece (2), and the gap between
the circular workpiece (2) and the gas-ring (41) is 0.5 mm˜2 mm.

[0062] The gas-ring (41) further includes a first member (414) and a
second member (415). The first member (414) is provided with a ring
section (4142) on the base section (4141), and the plural gas pores (411)
are provided on the ring section (4142). The second member (415) has a
ring portion (4151) one end of which has an annular flange (4152)
extending toward the axis, and the gas inlet opening (412) is provided on
the ring portion (4151). When the first member (414) is fastened with the
second member (415), one face of the base section (4141) of the first
member (414) abuts against one end of the ring portion (4151) of the
second member (415) and a gasket (416) is disposed therebetween.
Simultaneously, one end of the ring section (4142) of the first member
(414) abuts against one face of the ring portion (4151) of the second
member (415) and another gasket (417) is disposed therebetween. In this
manner, good gas-tight effect between the first member (414) and the
second member (415) can be achieved and output of gas stream from the gas
pores (411) can be ensured.

[0063] Another one preferred design of the annular gas-stream generating
device (4), as shown in FIGS. 7 and 8, is provided with an annular slit
(421) on the inner face of the gas-ring (42), which communicates with a
gas inlet opening (422). The gas inlet opening (422) is connected to a
gas supply source (423) such that the high pressure gas stream is
delivered out through the annular slit (421) to be an annular gas-stream.

[0064] In this case, the gas-ring (42) includes a first member (424) and a
second member (425). The first member (424) is provided with a ring
section (4242) on the base section (4241), while the second member (425)
has a ring portion (4251) one end of which has an annular flange (4252)
extending toward the axis, and the gas inlet opening (412) is provided on
the ring portion (4251). When the first member (424) is fastened with the
second member (425), one face of the base section (4241) of the first
member (424) abuts against one end of the ring portion (4251) of the
second member (425) and a gasket (426) is interposed therebetween.
Simultaneously, one end of the ring section (4242) of the first member
(424) abuts against one face of the ring portion (4251) of the second
member (425) and the slit (421) is formed therebetween. In this manner,
gas stream can be ensured to delivered out from the slit (421) between
the first member (424) and the second member (425).

[0065] Still another one preferred design of the annular gas-stream
generating device (4), as shown in FIG. 9, has a hollow cylinder body
(43). One end of the hollow cylinder body (43) has an opening (431)
having a diameter slightly larger than that of the circular workpiece (2)
such that the hollow cylinder body (43) can be put on the circular
workpiece (2). The other end of the hollow cylinder body (43) is an input
end (432) of high pressure gas. In this manner, annular gas-stream can be
produced at a slit formed between the opening (431) of the cylinder body
(43) and the circular workpiece (2).

[0066] When the annular gas-stream generating device (4) is implemented as
above, the annular gas-stream generating device (4) is utilized in film
coating operation on the outer surface of circular workpiece (2).

[0067] Yet another preferred design of the annular gas-stream generating
device (4), as shown in FIG. 10, is to provide an annular slit (441) on
the outer surface of a hollow cylinder body (44). The annular slit (441)
is in communication with the interior of the hollow cylinder body (44)
which is connected to a gas supply source (442) such that the high
pressure gas stream supplied from the gas supply source (442) is
delivered out through the annular slit (421) to be an annular gas-stream.
When the annular gas-stream generating device (4) is implemented as
above, the annular gas-stream generating device (4) is utilized in film
coating operation on the inner surface of circular workpiece (2).

[0068] When conducting coating on the surface of a circular workpiece (2),
taking the embodiment utilizing the first preferrind design of the
annular gas-stream generating device (4) as example for description
purpose, the circular workpiece (2) shown in FIG. 1 is disposed on the
rotating mechanism (1) and is fixed in place by the chuck (11) of the
rotating mechanism (1). In turn, the coating material is precoated on the
circular workpiece (2) from the discharge opening (61) of the feedstock
supply mechanism (6) Then, the circular workpiece (2) conducts
self-spinning, as shown in FIGS. 3 and 11. The high pressure gas supplied
from the gas supply source (413) enters into each gas pore (411) through
the gas inlet opening (412) of the gas-ring (41) and is ejected out of
each gas pore (411) from the interior, as shown in FIGS. 2 and 3. After
the translational mechanism (3) guides the gas-ring (41) by the guide
portion (31) toward the direction of the circular workpiece (2) and the
circular workpiece (2) then enters into the gas-ring (41), the high
pressure air ejected from the interior of the gas-ring (41) begins to
squeeze the coating material coated on the surface of the circular
workpiece (2) such that the coating material coated on the surface of the
circular workpiece (2) can become flat and uniform.

[0069] Referring to FIG. 12, the coating is conducted under the conditions
that the rotation speed of the circular workpiece (2) is 180 rpm, the
viscosity of polymer solution being 1000 cps, the pressure of high
pressure gas being 1 bar, and the gap between the annular gas-stream and
the circular workpiece (2) being 2 mm. The film thickness measurement is
conducted on several points of the surface of the circular workpiece (2)
as shown in FIG. 12 (c), and the measured data are shown in FIG. 12 (a)
expressed as table or in FIG. 12 (b) expressed as graph. It is confirmed
by these data that a film coating having even thickness can be obtained
by the technology of the present invention.

[0070] Further in the present embodiment, the rotating mechanism (1) is
exemplified to be a lathe as shown in FIG. 1. The coating material is
selected from: organic photoresist or UV resin, or any polymer material,
organic material, plastic material, compound of any two above materials,
or compound of more than two above materials. The high pressure gas can
be air or pure nitrogen gas.

[0071] Referring to FIG. 13, a schematic flow chart showing a preferring
embodiment of a method for conducting film coating on the surface of
spinning circular workpiece under action of gas pressure of the present
invention is shown. The method for conducting film coating on the surface
of spinning circular workpiece under action of gas pressure of. this
invention at least comprises following steps: [0072] (A) feeding coating
material onto the surface of circular workpiece; [0073] (B) driving the
circular workpiece in such a manner that the circular workpiece conduct
self-spinning at a predetermined speed with its axis as the center;
[0074] (C) passing the spinning circular workpiece through an annular
high pressure gas stream provided in radial direction of the circular
workpiece such that the coating material coated on the surface of the
circular workpiece is squeezed by the high pressure gas stream, the size
of which can be adjusted.

[0075] Based on the foregoing implementation, the the present invention
has at least the advantages set forth below.

[0076] 1. In the technology of conducting film coating on the surface of
spinning circular workpiece under action of gas pressure, the circular
workpiece is securely fixed on the rotating mechanism and is driven to
conduct self-spinning. The discharge opening is disposed above the
circular workpiece and the distance between the discharge opening and the
circular workpiece can be adjusted such that the coating material is
contacted with the spinning circular workpiece after it is output from
the discharge opening, and the coating matrial is precoated on the
surface of the circular workpiece by means of the self-spinning action of
the circular workpiece. The discharge opening also can wipe off redundant
material exceeding the height of the gap such that the coated material on
the surface of the circular workpiece has a contant initial thickness
dependent on the dimension of the gap between the discharge opening and
the circular workpiece. The faster the rotation speed is, the bigger the
frequency of circular workpiece's passage through the discharge opening
becomes and the better the uniformity is. Hence, the rotation speed of
the circular workpiece can determine the uniformity of the coating
material on the circular workpiece and the rotation speed can be adjusted
in digital manner.

[0077] 2. In the technology of conducting film coating on the surface of
spinning circular workpiece under action of gas pressure, the annular
gas-stream generating device is provided on the translational mechanism.
Hence, it is possible to set the translational movement speed of the
translational mechanism so as to control the speed of the annular
gas-stream generating device enclosing the circular workpiece.

[0078] 3. In the technology of conducting film coating on the surface of
spinning circular workpiece under action of gas pressure, the circular
workpiece is clamped on the rotating mechanism by the chuck thereof.
Therefore, it is not only easy in operation to hold the circular
workpiece in place but also the stability after holding is high.

[0079] 4. In the present invention, redundant coating material is guided
and overflowed toward the forward direction [transverse direction] and
the rotational direction [longitudinal direction]. Hence, the coating
status of the coating material is flat and waste of material is avoided.

[0080] 5. In the present invention, the contact portion between the nozzle
and the circular workpiece is formed to have a blade-like function so
that it can wipe off redundant coating material so as to reach the effect
of surface coating having good uniformity and flatness.